The invention relates to an exhaust gas turbocharger for an internal combustion engine including a compressor arranged in the intake duct and an exhaust gas turbine arranged in the exhaust duct of the engine in a turbine housing having an exhaust gas collection chamber from which the exhaust gas is directed onto the turbine wheel via a turbine inlet passage and a bypass arrangement for bypassing the turbine inlet passages.
DE 43 12 078 A1 discloses a turbocharged internal combustion engine with an exhaust gas turbine in the exhaust duct and a compressor in the intake duct of the internal combustion engine. By the compressor, the combustion air is compressed to an increased charge pressure with which the air is supplied to the cylinders of the engine. The compressor is provided with an auxiliary compressor which is mounted on the same shaft as the main compressor and is also driven by the exhaust gas turbine. The auxiliary compressor compresses recirculated exhaust gas to a higher pressure so that it can be admixed to the air mass flow supplied to the main compressor.
Because of the pre-compression of the exhaust gases in the auxiliary compressor, the spectrum of the operating conditions for the exhaust gas recirculation can be expanded. However, the additional auxiliary compressor requires relatively high construction expenditures.
U.S. Pat. No. 4,611,465 discloses an exhaust gas turbocharger for an internal combustion engine in the intake duct and an exhaust gas turbine in the exhaust duct of the engine. The exhaust gases of the internal combustion engine are supplied to a spiral exhaust gas collection chamber which is arranged in the turbine housing and from which the exhaust gases are admitted to the turbine wheel. The exhaust gases flow then via inlet passages to the turbine wheel for driving the turbine.
The internal combustion engine described in the U.S. Pat. No. 4,611,465 includes two cylinder banks whose exhaust gases are supplied separately to a respective turbine inlet channel of the exhaust gas turbine. From each turbine inlet channel an exhaust gas bypass line branches off and the two bypass lines extend to a common line section in which a charge pressure-controlled bypass valve is arranged. The common bypass line section is connected to the exhaust duct downstream of the exhaust gas turbine. The bypass valve is opened when the charge pressure in the intake duct downstream of the compressor exceeds a predetermined threshold so that then the exhaust gas is directly conducted to the exhaust duct while bypassing the turbine wheel.
The exhaust gas bypass line extends outside the turbine housing and joins the exhaust gas duct also outside the turbine housing downstream of the exhaust gas turbine. The bypass arrangement has the sole purpose of reducing an excess pressure or, respectively, avoiding the development of such an excess pressure. Other functions cannot be accomplished.
It is the object of the present invention to provide, with simple construction means, an exhaust gas turbocharger which, beyond its basic function as compressor for the combustion air of the internal combustion engine, can also serve as a gas supply pump.